The purpose for this research is to determine whether flumazenil is capable of producing a precipitated withdrawal syndrome in subjects who have received alprazolam for 3 days. Subjects with histories of drug abuse were given 2, 3, and 4 mg alprazolam (or placebo) on Monday, Tuesday, and Wednesday of each week for 4 weeks, and i.v. flumazenil or placebo on Thursday mornings. We recorded heart rate, vagal tone, self-report of benzodiazepine withdrawal, and the Profile of Mood States (POMS) before, during, and after the infusion. The preliminary results indicated that only subjects who received flumazenil after 3 days of alprazolam showed decreases in positive mood, increases in negative mood, and subjective withdrawal signs following the injection. The significance of these results is that they indicate that flumazenil is capable of precipitating withdrawal from a benzodiazepine. Thus, it may be possible to quickly detoxify individuals who are addicted to benzodiazepines by giving them a benzodiazepine antagonist.